Driving an electric vehicle (EV) is one of the most enjoyable ways to do right by Mother Earth. And charging that EV with power straight from the giant fusion reactor in the sky makes it doubly as fun. The question is, how much solar do you need to charge an EV? Another important question is: what does it cost to charge an EV with solar? Let’s find out together!

Take a look at this infographic (and if you want to learn more, we dig way down deep in the article below):

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How do all those numbers work?

This all depends on a few factors: the kind of electric vehicle (EV) you have, its battery capacity, and how much sun you get where you live. See, no EV is exactly like another, and solar production varies widely depending on where you are in the country. Let’s dig in and see what we come up with!

The car

What we call an EV is important to this calculation. We love plug-in hybrids as much as the next environmentally-minded guys, but let’s look at only those cars that can go at least 50 miles in pure electric mode. That’s enough to get most people to work and back every day, and cutting it off there helps make the list manageable—cutting out plug-in hybrids like the Prius and Honda Accord that can go just a couple dozen miles in EV mode.

Gee, the auto industry likes to pose its cars the same way for promo shots…

Pretty sweet list, huh? Now the things we care about when it comes to those cars is range (at least 50 miles electric, remember?) and battery size. We’re guessing you’re gonna be charging up from empty every day on some of the EVs with smaller batteries. If you’re driving your Tesla Model S 200 miles a day (which in L.A. County seems totally doable), it’s gonna take a lot more power than charging the Volt you drove from Bloomington, Minnesota to Minneapolis and back.

But comparing a 200-mile charge with a 50-mile charge doesn’t really tell you the right story. By calculating the ratio between each car’s battery size and range, you come up with a figure we’ll call Efficiency. That’s shorthand for energy required (kWh) to go one mile. Multiply that by a standard number of miles per day (let’s call it 50 to make it easy, and you’ve got Daily Charge (kWh/50mi). Simple!

Check out how the field ranks below (lower numbers are better. The Chevy Spark wins!

As you can see in the chart, the daily charge champion is the Chevrolet Spark, which needs just 11.5 kWh of juice to go 50 miles. The Tesla Model X tips the scales on the other side of the field, needing 18 kWh for its daily commute. The average daily charge for these electric vehicles is 15 kWh, which, multiplied by the nation’s average energy price of $.13/kWh means driving 50 miles will cost you just $1.95. Take THAT, gas prices! (But solar is even cheaper—read on to discover how much!)

So there you have it; now you know how much energy you’ll need for these guys every day. Of course those numbers go up or down based on usage, so to calculate your own needs, divide the number for your car by 50 and multiply by how many miles you drive every day.

Our next step is to figure how much solar you’ll need to make the electricity for your car.

The solar equipment

Yeah, I’d live there.

Right up front you have a choice to make. Do you want to be pragmatic and decide that a kWh of solar is a kWh of solar, whether it’s sent to the grid or used to charge your car’s battery? Or do you want to make absolutely sure every kWh used for the car comes from solar, even though it will cost more money?

The decision here is between a solar panel system on your roof, or solar plus storage: batteries that capture the kilowatt-hours and can be used to charge your ride when the sun isn’t shining. We pragmatists know that a kWh generated is a kWh earned, and we’re happy to send our panels’ generation off onto the grid and draw power from the utility company at night to charge our panels.

But calculating the cost of solar without battery storage and trying to figure out what percentage of that goes into charging your car if you plug it in at 5 pm or 7 pm is way too hard. We’re pragmatists, remember? So we’re going to assume since you have an EV and you want to charge it with solar, you’re gonna get some batteries to do it. Easy peasy. Sort of.

Electricity needs and the cost of solar+battery

Different parts of the country get different amounts of sun (duh), so you’ll need more panels to fill up your EV’s battery if you’re in Poughkeepsie than you will if you’re in Phoenix. Estimates of potential solar energy generation are based on how much sunshine reaches the rooftops where you are. Scientists and other cool people call this concept “insolation.”

All you do is find the number of the shaded area covering your home’s location, multiply it by .78 (for energy losses from wiring and AC/DC inversion) and multiply that number by the number of kW your solar system is rated to produce. Conversely, if you want to figure out how big a solar installation needs to be to produce your Tesla’s 18-kWh daily needs, you divide that number by the product of the area and .78, then divide the result by 365 days to get the final number.

Is your head spinning yet? Let’s work through an example:

You live in San Diego and you drive a Nissan Leaf 50 miles a day. How much energy do you need to charge it daily?

Your Nissan Leaf needs 14 kWh/day

A 1-kW solar installation in your city produces 1,482 kWh per year (get that number by taking 1900—the area of the map above where San Diego is, multiplied by the .78 for electricity losses)

That’s 4.06 kWh/day (1,482/365 days)

You need a 3.44-kW solar installation to feed your Leaf (14 kWh per day/4.06 kWh produced per kW of solar)

Now let’s break that down in a quick little table that shows how much solar you’d need to charge the average EV enough to go 50 miles (remember that’s 15 kWh, from the above table), depending on where you live in the US:

Size of solar installation needed to produce 15 kWh per day:

Pacific Northwest

Northeast

Midwest

South/
Southeast

Southwest

Average

System Size

7.2 kW

5.2 kW

4.7 kW

4.4 kW

4.3 kW

5.2 kW

# of 250W panels

29

21

19

18

18

21

Now we get to find out much each kWh will cost ya. Don’t look so excited.

The cost of solar

Let’s go with some simple assumptions for the cost of panels, inverter, batteries, and more. The nationwide average for the cost of solar equipment is $4/watt. You’ll also need two Tesla Powerwall 7-kWh batteries for charging the car, which cost $3,000 each plus $1,000 for installation. So we’ll multiply each system size by $4,000 and add $7,000.

But then there’s incentives, which vary all over the country. We’re going to make it easy on ourselves and assume at least the federal solar tax credit, which will knock 30% off the cost within the first year or three depending on how big a tax burden you have. So we’ll take the size from the last step, multiply it by $4 per watt, then take away 30% of the results for a cost after incentives.

Pacific Northwest

Northeast

Midwest

South/ Southeast

Southwest

Average

Size of solar installation needed:

7.2 kW

5.2 kW

4.7 kW

4.4 kW

4.3 kW

5.2 kW

# of 250W panels

29

21

19

18

18

21

Total Cost minus incentives:

$25,060

$19,460

$18,060

$17,220

$16,940

$19,348

Cost of solar per day:

$2.74

$2.13

$1.98

$1.89

$1.66

$2.12

per mile:

$0.05

$0.04

$0.04

$0.04

$0.04

$0.04

per kWh:

$0.18

$0.14

$0.13

$0.13

$0.12

$0.14

WHEW!

So there you have it. After incentives, solar+battery costs are just about as cheap electricity from the power company. You can have your EV and charge it with the sun. And by installing solar now, you’ll have that power for 25 years, meaning your next EV or three will be just as easy and inexpensive to charge. Or you could start selling that power to the utility company for retail rates, and probably make even more money that way.

35 thoughts on “How much does it cost to charge an electric car with solar power?”

We, as EV and solar advocates, do a disservice to our cause when we’re dismissive of plug-in hybrids, PHEVs. They can serve as the “gateway drug” to electric vehicles for the average person. 2 of the biggest sources of resistance to EVs, range anxiety and charging infrastructure, don’t exist for these vehicles. On a related note, one of the original and most compelling of plug-ins, the Chevy Volt, was left off your list. It has an all-electric range of 53 miles.

Thanks for your reply! We actually had the Chevy Volt on last year’s version of the EV solar charging roundup, but removed it this year because, though it does have significant all-electric range, it also has an ICE, and it’s actually one of the less-efficient electric drive systems out there.

Overall, you’re correct that plug-in hybrids can be a great way to partake in electric charging while eliminating worries about range and charging. Perhaps we’ll add an addendum to the article to reflect the possibilities of charging the smaller battery packs of plug-in hybrids.

you talk about the efficiency lost of 20% or so converting DC to AC. I’m sure there is more loss when converting AC back to DC for the car. My question. Is there a charging system that can take DC from the panel and provide DC to the car to charge? Or direct from the battery to the car?

My consideration as to solar was for the home needs first. The home used power each minute of the day. My system generates about 6,800 kwhours per year. Only after the house needs were met, I added a Nissan Leaf. The power needed for the car is variable as to use and other free sources of power in the area. My numbers are less than 200 kwhrs monthly. However, the car produces the greates savings as to gas, oil, filters, services.

Very few people benefit from these tax credits, since they are dollar for dollar and are targeted to government employees on a payroll rather than someone self employed with the operating expenses of a business or one who has other deductions.

I started with a 3.4 kW grid-tie solar system on a feed-in tariff program at $0.26 / kWh for 15 years. I buy off-peak on a PEV time-of-use program for $0.09. I produced about 10 kWh/day and charge my Ford Fusion Energi w/ 7.6 kWh battery. The sell/buy differential yields $1.70 plus a fully charged battery yielding 20 miles of pure EV.

Would anyone be interested in a solar panel kit for their electric car? If you did not drive far to work this would be helpful. For example using the roof and the hood for flexable panel mounting (conforms to the curves and looks good), one could add about 8 miles of use to whatever charge was in the batteries while the car is parked in the sun for 8 hours. This is not a lot of miles but might work for some.

Barry, if you are using California Gasoline prices in your analysis, you should also be deducting the $7,500 federal tax credit and the $2,500 California tax credit from the sale prices of the electric vehicles. The ROI gets a little better after a $10k price cut. Used electric prices will likely plummet as battery tech improves, making the ROI even more compelling on 3-5 year old electrics.

Definitely. Getting new customers is usually very expensive for a solar contractor, so if you have 6 lined up in a row, I bet you’ll be able to negotiate a good-sized discount for everybody. Their crews will spend more time there instead of driving all over creation to get to the next worksite, too. I can’t tell you how much to ask for, but I’d say somewhere around 5% seems reasonable. Good luck!

Ben, I had no idea you were using solar power in your calculations. That said $0.13 per kWh for a solar system is a bit high. I am a PV designer and have been designing PV since 2005 and what I see now adays for the levelized cost of energy on a typical rezi PV system is $0.085 to $0.10 per kWh over 20 years. Of course now we are talking about an electric car which costs more up front than a hybrid or regular gas powered car and the cost of the solar system after FTC and any rebates. The ROI on an electric car is terrible. Buy a PV system to zero out your home energy bill if you have net metering and get a Prius Eco to cut your travel expenses to the bone.

Thanks, Barry—that’s exactly the kind of advice people are looking for. This blog assumes the reader might want to have the bragging rights to all that solar powering their car’s battery, but you’re right. With net metering, simply offsetting the electricity you use is a much more cost-effective way to take advantage of the benefits of solar power.

Ryan Bergman says electric cars are just better. Better for what? Not much in my opinion. A Prius Eco kicks electric car butt in both cost per 100 miles and range. Also, electric cars are spartan and can’t handle anything but tooling around. Forget about hauling anything.

Pardon me if I step on any toes here. I just had to stop reading all the details about cost. There seems to be one very important thing that people don’t consider. Which would you rather use (or pay for), your Smartphone or a rotary dial up land line? You and I know that the smartphone dominates. Why? Because people pay MORE for BETTER. Also, late adapters wait until everyone else is doing it and they don’t want to be left behind. I’m almost 50 and I’ve been driving since 16 so I have decent amount of time behind the wheel. I drove a Leaf for 3 years and now have a Model S. Bottom line, electrics are better, and will only get better. And just like the 300-600 smartphone it will only continue to dominate in the future. Just like when the car out did the horse 100 years ago. Hope I didn’t offend too many people out there. It’s just how it is.

We recently attended earth day Texas and got a great price on a 5 KW solar system ($6,375 after all rebates and a $8,500 deduction for the company purchasing our Carbon Credit Incentive. I understand that is what they trade to other companies that need a deduction for their carbon output. I can’t figure out if that is a good deal or not or what the future implications are for our property. None of the other companies have said anything about this. Does anyone know anything about this?

I have 16Kw DC, it produces 21Mw/yr, a little low for the area because the panels are facing east and west, not south. But they do produce a lot of power, worth about $3k/yr. It is paid for in 2 years after subsidies and rebates. I don’t understand the part about ‘you could start selling that power to the utility company for retail rates’, I hear that all the time, from articles or from other people. I don’t know of any utility that does that. The best deal is net-net metering which I have, where you get a credit during the day for your surplus, so you can use it at night or next month to offset your usage from the grid, but at the end of the fiscal year it is zeroed out and you loose any remaining credits, you are not paid for them. The feed in tariffs where you sell your surplus to the utility is usually priced at the wholesale price of coal at about $.02/kw, then you pay retail at night when you get the power back from the grid, so it is about 1/2 the economic advantage of net-net metering. And people like Warren Buffet have vowed to put an end roof top solar and net-net metering, I hope they don’t but they usually get what they want. Look at what he pulled off with Nevada Energy early this year.

Let’s take a look at the upfront costs. How about the middle of the road fiat 500 vs the 500e. The 500 costs about $17000. The 500e costs $32000. So Gas is already ahead by $15000. Now, we know the cost of gas, as we purchase it from the gas station. What is the cost of solar, well if you don’t have panels you are looking at another 10-20K, let’s round this to 15K for the sake of simplicity. So added together, we are looking at an extra $30K up front so we can be solar. So lets take your numbers from the infographic. You say it will cost $1284 per year to drive a gas car. With that info, it means you will break even on your solar powered car in a mere 23 years! It’s not quite the deal you make it out to be. I think electric cars will be the future, and I can’t wait till we get there, but I think until the upfront costs go away, we aren’t going to get a lot of people forking over the money necessary to make that jump. Without lower prices, there is no consumer demand, and without consumer demand we won’t see enough extra charging stations around to make it reasonable. The end. ;)

Unfortunately if you live where I do, in the sparsely populated mountain west with major wind issues, an electric car is not guaranteed to get you very far, and in the winter, driving one would be tantamount to suicide. I certainly couldn’t make a 250 mile one way trip with the kids to go see my sick grandparents, much less expect to do a round trip in a day for emergencies. Electric cars may work for cities, but out here, they are nothing shy of ridiculous. Also, as a note, my house has solar panels for electricity. 20 panels requires a HUGE amount of space on the roof, all south facing. The salary of a chemical or computer engineer cannot pay for a house large enough to house those panels. Not feasible for the average person.

We have a 10 KW system on our roof interconnected to the grid here in Florida. The system cost $3/watt to install, but since we were able to get a big rebate from FPL and a smaller Federal tax credit, we expect to get pay back in 3-4 years. I’m a big fan of solar and electric vehicles, but in my opinion the missing piece in your analysis is the EV cost compared to a comparable gasoline care. With the much higher EV costs included in the analysis, I believe that the EV has a higher overall operating cost than a comparable gasoline vehicle. I’d love it if you can provide this analysis and prove me wrong.

Well this entire article’s conclusion is based on a kilowatt hour costing $0.13 and that is rubbish. Aggregate cost to most folks in my area is double that Which of course make the fuel cost more for the electric car. The miles per kWh is also B.S. for most models of electric car especially the Tesla models

Hey Barry, thanks for the reply. The $.13/kWh figure is the cost of the solar panels spread over 25 years, not the cost of the electricity from the utility company. It’s true that the average cost of electricity in the U.S. is $.13/kWh, but if your area is charged twice that (I’m guessing Massachusetts or California), you would actually do much better by using solar power to charge an EV than someone in, say, Georgia, where coal-based electricity can be had from the utility company for just $.10/kWh.

As far as miles/kWh for electric cars, are you saying that the figures for range (source from plugincars.com) are inflated?

Electrics have another huge advantage: Three moving part power trains that will likely last a lifetime. Newer battery science and technology is improving the length the batteries will last, and eventually we can expect batteries that will last more than 25 years. To get better mileage ICE cars increase parts counts dramatically. Expect them to fail sooner and more frequently.

Excellent point, Bruce! The costs of ownership for these cars are so low not just because they’re efficient. Considering how much dirty, oily, gasoline-filled air gets shuttled around inside ICE cars it’s a wonder they don’t break down even more often than they do. Ever had to clean out a MAF sensor (or any other part) on even post-2005 cars? It’s no fun.

The real issue here with calculating cost effectiveness of electric cars vs gasoline/petrol is not whether solar is cheaper for charging but if the high cost of ev battery ownership/rental is a non-starter compared to high mpg tradtional vehicles. I looked at evs when I recenly purchased a new car but the ev battery cost (half the price of the car) killed the idea completely for me. Unless they improve on battery life / cost, evs will mostly remain a more expensive option overall.

I have a TESLA S 90D and will need to generate 4500 KWhrs annually to offset 12K miles of gravel per year. My solar installer Vara Solar has proposed a 3.99K solar carport to supplement my existing 7.36K roof system which is nust about coverinv our existing household use.. with a per kWhr cost of 18.5 cents in our are of Nj.. is it really worth installing the power wall system even if my pv is REQUIRED to be grid connected for my SREC earnings each year? It zeems that the powerwall system will cost more than your quoted costs..And whefe is the amount of the 240Volt socket figured into these costs.. mine was about $2200 bundled in with my carport which is currently jammed up in local township variance and zoning code BS.. thanks, joe

You’re correct that you don’t need the Powerwall batteries at all. In fact, we’d recommend against them precisely because they add that expense to the final installed price. The only disadvantage is you can’t claim that your car is charged entirely with solar—only that your charging is offset with a similar amount of solar generation. Don’t get us wrong, though! Selling that electricity back to the grid and getting your SRECs is far better financially than paying extra to store electricity for your own use. Keep doing what you’re doing!

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